This invention relates to a semiconductor integrated circuit having a fuse-programmable control circuit for generating fuse-programmable signals, more particularly to an improved control circuit that simplifies the programming process when the fuse-programmable signals are not required.
Fuse-programmable control circuits are used, for example, to repair multi-megabit memories and other very-large-scale integrated circuits. Such repair can greatly increase production yields. Typically, the repair process involves programming a fuse-programmable memory to output a set of signals that cause redundant circuit elements to be selected in place of defective circuit elements.
One well-known type of fuse-programmable memory comprises a plurality of pairs of fusible links, the two links in each pair being coupled in series between a power-supply node and a ground node. An output signal is generated from a point between the two links. Programming is performed by cutting either the link near the power-supply node, making the output signal low, or the link near the ground node, making the output signal high.
A problem with this scheme is that to prevent unwanted current flow through the fuse-programmable memory, one fusible link in each pair must always be cut, even if the integrated circuit has no defective elements and requires no repair. In a defect-free integrated circuit, this need for a large number of link-cutting operations adds unnecessarily to the time, difficulty, and cost of manufacture.